1. Field of the Invention
The present invention relates to a discharged sheet accommodating tray in which sheets, such as films or printed papers, which have been discharged from a printer, a copier, or the like are stacked.
2. Description of the Related Art
Printing devices such as printers or copiers are equipped with a discharged sheet accommodating tray in which sheets such as printed papers, films or the like are stacked. A sheet for which printing has been completed and which is to be discharged from the printing device is discharged, by being nipped from above and below by conveying rollers, into a discharged sheet accommodating tray which is set beneath the sheet discharging section of the printing device so as to be slightly tilted upwardly with respect to the direction in which the sheets are discharged. The sheets are stacked in the discharged sheet accommodating tray in the order in which they are discharged.
Conventionally, the sheet stacking surface of the discharged sheet accommodating tray (i.e., the placement surface) has generally been formed only as a flat surface. Accordingly, when sheets discharged from the printing device are placed on the placement surface of the discharged sheet accommodating tray, the sheets become flat in conformance with the placement surface. A sheet discharged thereafter is pushed out while contacting the flat upper surface of the uppermost sheet among the sheets which have already been placed, i.e., the discharged sheets, and is placed on the discharged sheets. This process is repeated so as to stack discharged sheets on the discharged sheet accommodating tray.
However, the placement surface of the conventional discharged sheet accommodating tray is flat, and the sheets placed thereon also become flat in conformance with the flat placement surface. Therefore, as illustrated in FIG. 9, a sheet 1 discharged in succession is pushed out while contacting the flat upper surface of an uppermost sheet 3 of the stack of sheets already placed in a discharged sheet accommodating tray 5, and the flat surfaces of the sheet 1 and the sheet 3 slide. Due to the frictional force or electrostatic attractive force at this time, the sheet 1 which is being discharged and the uppermost sheet 3 stick together, and the sheet 1 being discharged either pushes the uppermost sheet 3 out from the discharged sheet accommodating tray 5 (so-called "pushing-falling"), or, as illustrated in FIG. 10, a leading end portion 1a of the sheet 1 being discharged sticks to the uppermost sheet 3, and the sheet 1 curls because it is discharged in a state of being stuck to the uppermost sheet 3. After the sheet 1 is discharged, it may fall from the discharged sheet accommodating tray 5 due to the elastic restoring force of the sheet 1 (so-called "curling-falling").
When thin plates or sheets formed from resin materials are discharged, a particularly great electrostatic attractive force is generated. As a result, a sheet being discharged may stick to the uppermost sheet of the sheets which have already been discharged, such that discharging becomes impossible and a sheet jam (jam error) occurs.